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Documentation/admin-guide: fixes for thunderbolt.rst

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Edits for grammar, punctuation, and a doubled-up word.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andreas Noever <andreas.noever@gmail.com>
Cc: Michael Jamet <michael.jamet@intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Yehezkel Bernat <yehezkel.bernat@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Randy Dunlap 2018-01-27 18:49:08 -08:00 committed by Jonathan Corbet
parent 9124bb8760
commit 54e36a2dc5
1 changed files with 33 additions and 33 deletions
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Documentation/admin-guide/thunderbolt.rst
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@ -3,13 +3,13 @@
=============
The interface presented here is not meant for end users. Instead there
should be a userspace tool that handles all the low-level details, keeps
database of the authorized devices and prompts user for new connections.
a database of the authorized devices and prompts users for new connections.
More details about the sysfs interface for Thunderbolt devices can be
found in ``Documentation/ABI/testing/sysfs-bus-thunderbolt``.
Those users who just want to connect any device without any sort of
manual work, can add following line to
manual work can add following line to
``/etc/udev/rules.d/99-local.rules``::
ACTION=="add", SUBSYSTEM=="thunderbolt", ATTR{authorized}=="0", ATTR{authorized}="1"
@ -20,7 +20,7 @@ vulnerable to DMA attacks.
Security levels and how to use them
-----------------------------------
Starting from Intel Falcon Ridge Thunderbolt controller there are 4
Starting with Intel Falcon Ridge Thunderbolt controller there are 4
security levels available. The reason for these is the fact that the
connected devices can be DMA masters and thus read contents of the host
memory without CPU and OS knowing about it. There are ways to prevent
@ -37,14 +37,14 @@ The security levels are as follows:
user
User is asked whether the device is allowed to be connected.
Based on the device identification information available through
``/sys/bus/thunderbolt/devices``. user then can do the decision.
``/sys/bus/thunderbolt/devices``, the user then can make the decision.
In BIOS settings this is typically called *Unique ID*.
secure
User is asked whether the device is allowed to be connected. In
addition to UUID the device (if it supports secure connect) is sent
a challenge that should match the expected one based on a random key
written to ``key`` sysfs attribute. In BIOS settings this is
written to the ``key`` sysfs attribute. In BIOS settings this is
typically called *One time saved key*.
dponly
@ -78,7 +78,7 @@ When a device is plugged in it will appear in sysfs as follows::
/sys/bus/thunderbolt/devices/0-1/unique_id - e0376f00-0300-0100-ffff-ffffffffffff
The ``authorized`` attribute reads 0 which means no PCIe tunnels are
created yet. The user can authorize the device by simply::
created yet. The user can authorize the device by simply entering::
# echo 1 > /sys/bus/thunderbolt/devices/0-1/authorized
@ -86,7 +86,7 @@ This will create the PCIe tunnels and the device is now connected.
If the device supports secure connect, and the domain security level is
set to ``secure``, it has an additional attribute ``key`` which can hold
a random 32 byte value used for authorization and challenging the device in
a random 32-byte value used for authorization and challenging the device in
future connects::
/sys/bus/thunderbolt/devices/0-3/authorized - 0
@ -99,12 +99,12 @@ future connects::
Notice the key is empty by default.
If the user does not want to use secure connect it can just ``echo 1``
If the user does not want to use secure connect they can just ``echo 1``
to the ``authorized`` attribute and the PCIe tunnels will be created in
the same way than in ``user`` security level.
the same way as in the ``user`` security level.
If the user wants to use secure connect, the first time the device is
plugged a key needs to be created and send to the device::
plugged a key needs to be created and sent to the device::
# key=$(openssl rand -hex 32)
# echo $key > /sys/bus/thunderbolt/devices/0-3/key
@ -121,27 +121,27 @@ device using the same key::
If the challenge the device returns back matches the one we expect based
on the key, the device is connected and the PCIe tunnels are created.
However, if the challenge failed no tunnels are created and error is
However, if the challenge fails no tunnels are created and error is
returned to the user.
If the user still wants to connect the device it can either approve
the device without a key or write new key and write 1 to the
If the user still wants to connect the device they can either approve
the device without a key or write a new key and write 1 to the
``authorized`` file to get the new key stored on the device NVM.
Upgrading NVM on Thunderbolt device or host
-------------------------------------------
Since most of the functionality is handled in a firmware running on a
Since most of the functionality is handled in firmware running on a
host controller or a device, it is important that the firmware can be
upgraded to the latest where possible bugs in it have been fixed.
Typically OEMs provide this firmware from their support site.
There is also a central site which has links where to download firmwares
There is also a central site which has links where to download firmware
for some machines:
`Thunderbolt Updates <https://thunderbolttechnology.net/updates>`_
Before you upgrade firmware on a device or host, please make sure it is
the suitable. Failing to do that may render the device (or host) in a
Before you upgrade firmware on a device or host, please make sure it is a
suitable upgrade. Failing to do that may render the device (or host) in a
state where it cannot be used properly anymore without special tools!
Host NVM upgrade on Apple Macs is not supported.
@ -151,7 +151,7 @@ Thunderbolt device so that the host controller appears. It does not
matter which device is connected (unless you are upgrading NVM on a
device - then you need to connect that particular device).
Note OEM-specific method to power the controller up ("force power") may
Note an OEM-specific method to power the controller up ("force power") may
be available for your system in which case there is no need to plug in a
Thunderbolt device.
@ -171,7 +171,7 @@ it comes back the driver notices it and initiates a full power cycle.
After a while the host controller appears again and this time it should
be fully functional.
We can verify that the new NVM firmware is active by running following
We can verify that the new NVM firmware is active by running the following
commands::
# cat /sys/bus/thunderbolt/devices/0-0/nvm_authenticate
@ -179,38 +179,38 @@ commands::
# cat /sys/bus/thunderbolt/devices/0-0/nvm_version
18.0
If ``nvm_authenticate`` contains anything else than 0x0 it is the error
If ``nvm_authenticate`` contains anything other than 0x0 it is the error
code from the last authentication cycle, which means the authentication
of the NVM image failed.
Note names of the NVMem devices ``nvm_activeN`` and ``nvm_non_activeN``
depends on the order they are registered in the NVMem subsystem. N in
depend on the order they are registered in the NVMem subsystem. N in
the name is the identifier added by the NVMem subsystem.
Upgrading NVM when host controller is in safe mode
--------------------------------------------------
If the existing NVM is not properly authenticated (or is missing) the
host controller goes into safe mode which means that only available
functionality is flashing new NVM image. When in this mode the reading
host controller goes into safe mode which means that the only available
functionality is flashing a new NVM image. When in this mode, reading
``nvm_version`` fails with ``ENODATA`` and the device identification
information is missing.
To recover from this mode, one needs to flash a valid NVM image to the
host host controller in the same way it is done in the previous chapter.
host controller in the same way it is done in the previous chapter.
Networking over Thunderbolt cable
---------------------------------
Thunderbolt technology allows software communication across two hosts
Thunderbolt technology allows software communication between two hosts
connected by a Thunderbolt cable.
It is possible to tunnel any kind of traffic over Thunderbolt link but
It is possible to tunnel any kind of traffic over a Thunderbolt link but
currently we only support Apple ThunderboltIP protocol.
If the other host is running Windows or macOS only thing you need to
do is to connect Thunderbolt cable between the two hosts, the
``thunderbolt-net`` is loaded automatically. If the other host is also
Linux you should load ``thunderbolt-net`` manually on one host (it does
not matter which one)::
If the other host is running Windows or macOS, the only thing you need to
do is to connect a Thunderbolt cable between the two hosts; the
``thunderbolt-net`` driver is loaded automatically. If the other host is
also Linux you should load ``thunderbolt-net`` manually on one host (it
does not matter which one)::
# modprobe thunderbolt-net
@ -220,12 +220,12 @@ is built-in to the kernel image, there is no need to do anything.
The driver will create one virtual ethernet interface per Thunderbolt
port which are named like ``thunderbolt0`` and so on. From this point
you can either use standard userspace tools like ``ifconfig`` to
configure the interface or let your GUI to handle it automatically.
configure the interface or let your GUI handle it automatically.
Forcing power
-------------
Many OEMs include a method that can be used to force the power of a
thunderbolt controller to an "On" state even if nothing is connected.
Thunderbolt controller to an "On" state even if nothing is connected.
If supported by your machine this will be exposed by the WMI bus with
a sysfs attribute called "force_power".